The kit in question, a role-playing game maker, allowed users to design their own Pokémon adventures. Now, Nintendo has gone after a new target: 11-year old fan game creator, Pokémon Essentials. In the last few months alone, it filed several lawsuits against emulation sites, and is believed to have indirectly pressured ROM site EmuParadise into shutting down.
Nintendo has gained a bit of a reputation for its strict copyright policy.